The overall objective of the proposal is to produce derivatives of cardiac glycoside and estradiol which are capable of binding a radionuclide. In the case of radioiodine a phenol or imidazole group will be bound. These derivatives will be tested as analogs for the parent biochemical. In the current year we proposed the synthesis of four derivatives of estradiol: 2-iodoestradiol, 2-idohexestrol, tyrosine methyl ester amide of 17 estradiol hemisuccinate, and tyrosine methyl ester amide of estradiol-6-(O carboxmethyl) oxime. In order to evaluate these estrogen derivatives as possible diagnostic agents, two experimental methods will be used - in vitro competitive binding using H3 estradiol and in vivo tissue distribution.